WO2011098149A1

WO2011098149A1 - Methods, apparatuses and related computer program product for a seamless handover operation

Info

Publication number: WO2011098149A1
Application number: PCT/EP2010/051862
Authority: WO
Inventors: Laszlo Janosi
Original assignee: Nokia Siemens Networks Oy
Priority date: 2010-02-15
Filing date: 2010-02-15
Publication date: 2011-08-18

Abstract

A network entity (2023, 2024) transmits coding / decoding information currently selected according to a first communication technology, the coding / decoding information being intended for use in a handover procedure from the first technology to a second technology different from the first technology. A network entity (2021) receives (S4-1) the coding / decoding information currently selected according to the first communication technology. In case a handover operation from the first technology to the second technology is decided (S4-3) to be performed, a request comprising the coding / decoding information currently selected is transmitted (S4-4). The request is received (S5-1) by a network entity (2026), which reserves (S5-2) at least one communication re-source of the second technology according to the coding / decoding information currently selected.

Description

TITLE OF THE INVENTION

METHODS, APPARATUSES AND RELATED COMPUTER PROGRAM PRODUCT FOR A SEAMLESS HANDOVER OPERATION

FIELD OF THE INVENTION

An example of the present invention relates to a seamless handover operation. More specifically, the example of the present invention relates to methods, apparatuses and a re^¬ lated computer program product for a seamless handover opera^¬ tion. The example of the present invention may be applicable e.g. to EPS (evolved packet system), which may be regarded as a successor of GPRS (general packet radio system) . EPS core network functions may reside in a MME (mobility management entity), a PDN-GW (packet data network gateway) and/or an S- GW (serving gateway) .

BACKGROUND

Fig. 1 shows a general EPS architecture. As shown in Fig. 1, a communication network 100 may comprise a UE (user equipment) 101, an E-UTRAN (evolved universal mobile telecommuni^¬ cation system terrestrial radio access network) 102, a MME 103, a SGSN (serving GPRS support node) 104, a HSS (home sub^¬ scriber server) 105, a S-GW 106, a PDN-GW 107, a PCRF (policy and charging rules function) 108 and the operator's internet protocol services 109. As indicated by connections between the functional blocks of the network elements 101 to 109, a network element may commu^¬ nicate with another network element via respective inter^¬ faces, for example the LTE (long term evolution) -Uu interface between the UE 101 and the E-UTRAN 102, the Sl-MME interface between the E-UTRAN 102 and the MME 103, the Sl-U interface between the E-UTRAN 102 and the S-GW 106, the S3 interface between the MME 103 and the SGSN 104, the S4 interface be^¬ tween the SGSN 104 and the S-GW 106, the S5/S8 interface be^¬ tween the S-GW 106 and the PDN-GW 107, the S6a interface be^¬ tween the MME 103 and the HSS 105, the S10 interface between the MME 103 and another MME (not shown), the Sll interface between the S-GW 106, the Gx interface between the PDN-GW 107 and the PCRF 108, the Rx interface between the PCRF 108 and the operator's IP services (e.g. IMS (internet protocol mul^¬ timedia subsystem)) 109 and the SGi interface between the PDN-GW 107 and the operator's IP services 109.

Fig. 2 shows a general PCC (policy and charging control) ar^¬ chitecture. As shown in Fig. 2, a communication network 1000 (which may be identical to the communication network 100 shown in Fig. 1) comprises a SPR (subscription profile repository) 1001, an AF (application function) 1002, a PCRF

1003, a BBERF (Bearer Binding and Event Reporting Function)

1004, a PCEF (policy control enforcement function) 1005, an OCS (online charging system) 1006 and an OFCS (offline charg- ing system) 1007.

As indicated by connections between the functional blocks of the network elements 1001 to 1007, a network element may com^¬ municate with another network element via respective inter- faces, for example the Sp interface between the SPR 1001 and the PCRF 1003, the above Rx interface between the AF 1002 and the PCRF 1003, the Gxx interface between the PCRF 1003 and the BBERF 1004, the above Gx interface between the PCRF 1003 and the PCEF 1005 residing in a gateway, the Gy interface be- tween the PCEF 1005 and the OCS 1006 and the Gz interface be^¬ tween the gateway of the PCEF 1005 and the OFCS 1007.

The PCC System may provide QoS (quality of service) parame^¬ ters and charging rules for EPS in order to allow EPS to re- serve the resources required by the user for a given packet data service and to charge the usage of those resources.

The AF 1002 may reside in the service domain (packet data network) and may provide information about service level re- source requirements to the PCRF 1003. The PCRF 1003 may run a business logic, the input to the PCRF 1003 being the informa^¬ tion received from the AF 1002 and subscription information received from the SPR 1001. As a result, the PCRF 1003 may provide QoS policy and charging data to the PCEF 1005 or the BBERF 1004.

In EPS architecture, the PDN-GW 107 shown in Fig. 1 may act as the PCEF 1005 and the S-GW 106 shown in Fig. 1 may act as the BBERF 1004.

A roaming architecture may be supported by the PCC System, so that the serving PCRF 1003, PCEF 1005, BBERF 1004 and AF 1002 may reside in a visited PLMN (Public Land Mobile Network) . In that case, an S9 interface may be defined between the home PCRF 1003 and a visited PCRF (not shown) in order to transfer subscription information from the SPR 1001.

Fig. 3 shows the IMS reference architecture. For brevity of this description, a detailed description of the IMS reference architecture is omitted. IMS is a 3GPP (3^rd generation part^¬ nership project) service domain system e.g. for providing VoIP (Voice over IP), IM (Instant Messaging) and other IP based services for end users. EPS may serve as an access net^¬ work to IMS Services. The AF 1002 shown in Fig. 2 may be im- plemented by a P-CSCF shown in Fig. 3 in the IMS Architec^¬ ture .

Further, SRVCC (single radio voice call continuity) is pro^¬ vided e.g. for ensuring seamless handover of VoIP calls e.g. from IMS to the CS mobile network. Another interface has been introduced between the MME and a MSC Server (to be described with reference to Figs. 4 and 5) for this purpose, the inter^¬ face's name being Sv.

In consideration of the above, according to the example of the present invention, methods, apparatuses and a related computer program product for a seamless handover operation are provided.

In this connection, the examples of the present invention en- able one or more of the following:

- Transferring information about the currently used codec from the MME to the MSS during SRVCC;

- Enabling optimal CS side resource reservation;

- Dispensing with a need for transcoders after handover on user plane, thus avoiding additional resource consumption and voice quality degradation, or avoiding mid-call codec nego^¬ tiation and modification, thus in turn avoiding a resource consuming procedure on signaling path.

- Avoiding the necessity of support of selected codec infor- mation from the UE, which would mean that support is required from many vendors and even more models, thus resulting in a generic support for an EPS core based solution, because much less variation of vendors/models is present;

- Avoiding a MSC Server based solution, thus avoiding that the codec is known only after the CS bearer has been already established on the radio access, and possibly to another MSC Server, if the target radio area is controlled by a different MSC Server. Consequently, an additional codec modification procedure once the codec is known or transcoder usage is avoided;

- Providing the MSS with the codec information from the Relocation Request, so that the MSS may use the codec informa^¬ tion already at CS bearer reservation phase. BRIEF DESCRIPTION OF THE DRAWINGS The example of the present invention is described herein be^¬ low with reference to the accompanying drawings, in which:

Fig. 1 shows the above-described general EPS architecture;

Fig. 2 shows the above-described general PCC architecture;

Fig. 3 shows the above-described IMS reference architecture; Fig. 4 shows methods for a seamless handover operation ac^¬ cording to the example of the present invention; and

Fig. 5 shows apparatuses for a seamless handover operation according to the example of the present invention.

DETAILED DESCRIPTION OF THE EXAMPLE OF THE PRESENT INVENTION

The example of the present invention is described herein be^¬ low by way of example with reference to the accompanying drawings.

It is to be noted that for this description, the terms

"internet protocol multimedia subsystem codec information; internet protocol multimedia subsystem; circuit switched mo- bile network; single radio voice call continuity handover op^¬ eration; and forward relocation request" are examples for "coding/decoding information; first communication technology; second communication technology; handover operation; and request", respectively, without restricting the latter-named terms to the special technical or implementation details im^¬ posed to the first-named terms.

Fig. 4 shows the methods for a seamless handover operation according to the example of the present invention. Signaling between elements may be indicated in horizontal direction, while time aspects between signaling may be reflected in the vertical arrangement of the signaling sequence as well as in the sequence numbers. It is to be noted that the time aspects indicated in Fig. 4 do not necessarily restrict any one of the method steps shown to the step sequence outlined. This applies in particular to method steps that are functionally disjunctive with each other. Within Fig. 4, for ease of description, means or portions which may provide main functionalities are depicted with solid functional blocks or arrows and/or a normal font, while means or portions which may pro- vide optional functions are depicted with dashed functional blocks or arrows and/or an italic font.

In other words, Fig. 4 shows an implementation example of the present invention relating to a VoIP call in EPS from the QoS handling point of view, and a SRVCC handover that to the CS mobile network.

As shown in Fig. 4, a communication system 200 may comprise a UE 201 and a network 202. In turn, the network 202 may fur- ther comprise the MME 2021, the PDN-GW/S-GW 2022, the PCRF 2023, the P-CSCF 2024 (which may act as the AF) , a VoIP do^¬ main 2025 in IMS, a MSC (mobile switching center) server or MSS 2026 and a CS RAN (circuit switched radio access network) 2027.

In optional preparatory steps 1 to 3, the UE 201 may be at^¬ tached to the EPS, the default bearer may be reserved and the UE 201 may be registered e.g. to IMS (step 1) . When the UE 201 starts e.g. a VoIP session (step 2), the UE 201 may send its supported voice codec information in SDP (session de^¬ scription protocol) (SDP offer) encapsulated e.g. in SIP INVITE message (step 3) . The VoIP domain 2025 may send its own supported codecs e.g. in SDP answer encapsulated e.g. into an appropriate SIP message. In an optional step Sl-la, e.g. the P-CSCF/AF 2024 may per^¬ form determining, if coding/decoding information currently selected cannot be determined, to use, as the coding/decoding information currently selected, the first common cod- ing/decoding information according to a session description protocol offer and answer scheme.

Alternatively, in an optional step Sl-lb, e.g. the P-CSCF/AF 2024 may perform transmitting more than one candidate for the coding/decoding information currently selected.

In steps S2-1 and S2-2, e.g. the PCRF 2023 may perform re^¬ ceiving and transmitting (or relaying) the coding/decoding information (e.g. selected IMS codec) currently selected ac- cording to a first communication technology (e.g. IMS), the coding/decoding information being intended for use during a handover procedure from the first technology to a second technology (e.g. CS) different from the first technology. Likewise, in steps S3-1 and S3-2, e.g. the PDN-GW/S-GW 2022 may perform receiving and transmitting (or relaying) the coding/decoding information (e.g. selected IMS codec) currently selected . As a development pertaining to the PDN-GW/S-GW 2022, the PCRF 2023 and the P-CSCF/AF 2024, the coding/decoding information currently selected may constitute a first applied content of a service-to-access-control container. In this case, the ser^¬ vice-to-access-control container may be transmitted and re- ceived transparently.

Accordingly, in step S4-1, e.g. the MME 2021 may perform receiving the coding/decoding information (e.g. selected IMS codec) currently selected according to the first communica- tion technology (e.g. IMS). In optional step 4, the MME 2021 may ask the radio access network to reserve resources with the given Policy informa^¬ tion . Then, in an optional step S4-2, e.g. the MME 2021 may perform storing the coding/decoding information currently selected.

In optional steps 5 and 6, when a radio bearer is reserved, and the S-GW and PDN-GW 2022 has reserved core side bearer as well, the VoIP session is established and voice sample pack^¬ ages can flow on the reserved bearers.

Accordingly, in step S4-3, e.g. the MME 2021, together with the E-UTRAN 102, may perform deciding on whether a handover operation (e.g. SRVCC handover) from the first technology to a second technology (e.g. CS) different from the first tech^¬ nology is to be performed.

Further, in step S4-4, e.g. the MME 2021 may perform initiat- ing, if the deciding is affirmative, a request (e.g. Forward Relocation request) comprising the coding/decoding information currently selected. In turn, in step S5-1, e.g. the MSS 2026 may perform receiving the request comprising the coding/decoding information currently selected depending on the decision on whether the handover operation from the first technology to the second technology (CS) is to be performed.

Finally, in step S5-2, e.g. the MSS 2026 may perform reserv^¬ ing at least one communication resource (e.g. bearer) of the second technology according to the coding/decoding informa^¬ tion currently selected.

Optionally, as shown in steps 7 to 9, the MSS 2026 may redi^¬ rect the existing IMS session to itself (step 7) and to wait for handover execution (step 8) . The request may contain a supported coded List of the UE 201. When CS side resources are reserved, the MME 2021 can command the UE 201 to adapt to the CS RAN 2027. After the UE 201 camps on the CS RAN 2027, conversation may continue on CS side (step 9) . As a development pertaining to all the above entities (i.e. the MME 2021, the PDN-GW/S-GW 2022, the PCRF 2023, the P- CSCF/AF 2024 and the MSS 2026), the transmitting and receiving of the coding/decoding information currently selected may be performed based on policy and charging control-related in- terfaces. In this case, the policy and charging control- related interfaces may comprise the Rx, Gx, Gxx, S5/S8, Sll and/or S9 interfaces. It is to be noted that Sll is an

Evolved Packet Core related interface between MME and S-GW. It has PCC roles, too, but it serves other purposes as well (e.g. bearer control).

Fig. 5 shows apparatuses (e.g. the MME 2021, the PDN-GW/S-GW 2022, the PCRF 2023, the P-CSCF/AF 2024 and the MSS 2026) for a seamless handover operation according to the example of the present invention. Within Fig. 5, for ease of description, means or portions which may provide main functionalities are depicted with solid functional blocks or arrows and/or a nor^¬ mal font, while means or portions which may provide optional functions are depicted with dashed functional blocks or ar- rows and/or an italic font.

The MME 2021 may comprise a CPU (or circuitry) 20211, a memory (or means for storing) 20212, a transmitter (or means for transmitting) 20213, a receiver (or means for receiving) 20214 and a decider (or means for deciding) 20215.

The PCRF 2023 may comprise a CPU (or circuitry) 20231, a mem^¬ ory 20232, a transmitter (or means for transmitting) 20233 and an optional receiver (or means for receiving) 20234. For reasons of descriptive briefness, the internal structure of the PDN-GW/S-GW 2022 is not explicitly shown in Fig. 5. However, it is to be noted that the PDN-GW/S-GW 2022 may have the same or similar structure as the PCRF 2023 concerning at least the above described reception/transmission capabili^¬ ties .

The P-CSCF/AF 2024 may comprise a CPU (or circuitry) 20241, a memory (or means for storing) 20242, a transmitter (or means for transmitting) 20243, an optional receiver (or means for receiving) 20244 and an optional determiner (or means for determining) 20245.

Finally, the MSS 2026 may comprise a CPU (or circuitry) 20261, a memory 20262, an optional transmitter (or means for transmitting) 20263, a receiver (or means for receiving) 20264 and an optional reserver (or means for reserving) 20265. As indicated by the dashed extensions of the functional blocks of the CPUs 20211, 20241 and 20261, the means for de^¬ ciding 20215 of the MME 2021, the means for determining 20245 of the P-CSCF/AF 2024 and the means for reserving 20265 of the MSS 2026 (and the respective means for transmitting

20213, 20243 and 20263 and the respective means for receiving 20214, 20244 and 20264) may be functionalities running on the CPUs 20211, 20241 and 20261 of the MME 2021, the P-CSCF/AF 2024 and the MSS 2026, or may alternatively be separate func^¬ tional entities or means.

The CPUs 20x1 (wherein x = 21, 23, 24 and/or 26) may respec^¬ tively be configured, for example by software residing in the memory 20x2, to process various data inputs and to control the functions of the memories 20x2, the means for transmit- ting 202x3 and the means for receiving 20x4 (as well as the means for deciding 20215 of the MME 2021, the means for de- termining 20245 of the P-CSCF/AF 2024 and the means for reserving 20265 of the MSS 2026) . The memories 20x2 may serve e.g. for storing code means for carrying out e.g. the methods according to the example of the present invention, when run e.g. on the CPUs 20x1. It is to be noted that the means for transmitting 20x3 and the means for receiving 20x4 may alternatively be provided as respective integral transceivers. It is further to be noted that the transmitters/receivers may be implemented i) as physical transmitters/receivers for

transceiving e.g. via the air interface (e.g. between the UE 201 and the MME 2021), ii) as routing entities e.g. for transmitting/receiving data packets e.g. in a PS (packet switching) network (e.g. between the network elements 20x when disposed as separate network entities) , iii) as func- tionalities for writing/reading information into/from a given memory area (e.g. in case of shared/common CPUs or memories e.g. of the network elements 20x when disposed as an integral network entity) , or iv) as any suitable combination of i) to iii) .

For example, the means for determining 20245 of the P-CSCF/AF 2024 may perform determining, if coding/decoding information currently selected cannot be determined, to use, as the cod^¬ ing/decoding information currently selected, the first common coding/decoding information according to a session description protocol offer and answer scheme.

Alternatively, e.g. the means for transmitting 20243 of the P-CSCF/AF 2024 may perform transmitting more than one candi- date for the coding/decoding information currently selected.

Then, e.g. the means for receiving 20234 and the means for transmitting 20233 of the PCRF 2023 may perform receiving and transmitting (or relaying) the coding/decoding information (e.g. selected IMS codec) currently selected according to a first communication technology (e.g. IMS), the cod- ing/decoding information being intended for use in a handover procedure from the first technology to a second technology (e.g. CS) different from the first technology. Likewise, e.g. the means for receiving and transmitting (not shown) of the PDN-GW/S-GW 2022 may perform receiving and transmitting (or relaying) the coding/decoding information (e.g. selected IMS codec) currently selected. As a development pertaining to the PDN-GW/S-GW 2022, the PCRF 2023 and the P-CSCF/AF 2024, the coding/decoding information currently selected may constitute a first applied content of a service-to-access-control container. In this case, the ser^¬ vice-to-access-control container may be transmitted and re- ceived transparently.

Accordingly, e.g. the means for receiving 20214 of the MME 2021 may perform receiving the coding/decoding information (e.g. selected IMS codec) currently selected according to the first communication technology (e.g. IMS).

Then, e.g. the means for storing 20212 of the MME 2021 may perform storing the coding/decoding information currently selected .

Accordingly, e.g. the means for deciding 20215 of the MME 2021, together with E-UTRAN 102, may perform deciding on whether a handover operation (e.g. SRVCC handover) from the first technology to a second technology (e.g. CS) different from the first technology is to be performed.

Further, e.g. the means for transmitting 20213 of the MME 2021 may perform transmitting, if the deciding is affirmative, a request (e.g. Forward Relocation request) comprising the coding/decoding information currently selected. In turn, e.g. the means for receiving 20264 of the MSS 2026 may per- form receiving the request comprising the coding/decoding information currently selected depending on the decision on whether the handover operation from the first technology to the second technology (e.g. CS) is to be performed.

Finally, e.g. the means for reserving 20265 of the MSS 2026 may perform reserving at least one communication resource (e.g. bearer) of the second technology according to the cod^¬ ing/decoding information currently selected.

As a development pertaining to all the above entities (i.e. network elements 2021 to 2024), the transmitting and receiving of the coding/decoding information currently selected may be performed based on policy and charging control-related in- terfaces. In this case, the policy and charging control- related interfaces may comprise the Rx, Gx, Gxx, S5/S8, Sll (EPC related interface) and/or S9 interfaces.

Furthermore, at least one of, or more of the above-described means for receiving 20214, 20234, 20244, 20264, means for deciding 20215, means for transmitting 20213, 20233, 20243, 20263, means for storing 20212, 20242, means for determining 20245, means for reserving 20265 as well as the MME 2021, the PDN-GW/S-GW 2022, the PCRF 2023, the P-CSCF/AF 2024 and the MSS 2026 or the respective functionalities carried out, may be implemented as a chipset, module or subassembly.

Finally, the example of present invention also relates to a system which may comprise the MME 2021, the PDN-GW/S-GW 2022, the PCRF 2023, the P-CSCF/AF 2024 and the MSS 2026 according to the above-described example of the present invention.

Without being restricted to the details following in this section, the examples of the present invention may be summa- rized as follows: A currently selected codec may be delivered to MME from AF e.g. on the path of Policy Control procedures. That is, AF may send the selected codec to the PCRF, and the PCRF may send not only Policy and Charging control information over the Gx/Gxx interface, but delivers the selected codec as well. The PDN-GW sends the information to S-GW over S5/S8 interface. The S-GW may send the information transparently to MME, and the MME may store the information e.g. to the given subscriber's session/bearer. When the SRVCC is to be exe- cuted, the MME may send the selected codec information to MSS e.g. over the Sv interface e.g. in Forward Relocation Re^¬ quest. The MSS may then use the received codec information in its CS bearer establishment procedures. The used transfer method from the AF to the MME (e.g. over interfaces between PCRF, PDN-GW, S-GW) may be implemented so as to be prepared for other future usage, e.g. a service-to- access-control container may be implemented, and selected co^¬ dec information may be the first applied content in it. The container may be delivered from AF to MME transparently, i.e. other network elements, like PCRF, PDN-GW and S-GW may pass the container transparently.

The AF may investigate the SIP messages and when it has codec information from both sides, which are then sent to PCRF over Rx interface. The PCRF may execute its business logic to de^¬ termine the required QoS level and bandwidth information. QoS level, bandwidth information and other data may be sent to the PDN-GW or S-GW over Gx or Gxx interfaces, respectively. The PDN-GW may send the request to S-GW over S5/S8 interface. The S-GW may send the bearer request to MME, policy rules may be sent to the MME over Sll interface.

The implementation may support the delivery of the container e.g. over PCC related interfaces, such as Rx, Gx, Gxx, S5/S8, Sll and S9 interfaces. The AF may send its known selected co- dec information in the container. If no exact selected codec is known, the AF may consider the first common codec e.g. of the SDP offer and answer. Alternatively, the AF may send com^¬ mon, voice part of offered and answered SDPs, i.e. more than one codec may be included in the container. The MME may store the received codec information and send the information via the Sv interface to the MSC Server (MSS) e.g. when SRVCC is triggered. The MSS may then use the received codec informa^¬ tion in its CS bearer reservations, as if the codec informa- tion was received form UE itself.

[Further examples]

For the purpose of the present invention as described herein above, it should be noted that

- a circuitry may refer to at least one of, or hybrids of the following:

(a) to pure hardware circuit implementations (such as im^¬ plementations purely in analog and/or digital circuitry), and (b) to combinations of circuits and software (and/or firmware) , such as (as applicable) :

(i) a combination of processor ( s ) , or

(ii) portions of processor ( s ) /software (including digital signal processor ( s )) , software and memory (or memo- ries) that work together to cause an apparatus as defined hereinabove to perform various functions, and

(c) to circuits, such as (micro) processor (s) or a portion of (a) (micro) processor (s) that require software and/or firm^¬ ware for operation even if the software or firmware is not physically present;

- a processor may be any processing unit, such as CPU, arithmetic and logic unit (ALU) , microprocessor unit (MPU) , digital signal processor (DSP) etc., be it a single core processor, dual core processor or multi-core processor;

- a program may be embodied by or on any computer program (product), computer readable medium, processor ( s ) , memory (or memories) , circuitry, circuits, random access memory (RAM), read-only memory (ROM) and/or data structure ( s ) , be it e.g. as compiled/non-compiled program (source) code, executa^¬ ble object, (meta) file or the like;

- an access technology may be any technology by means of which a user equipment can access an access network (or base station, respectively) . Any present or future technology, such as WiMAX (Worldwide Interoperability for Microwave Ac^¬ cess) or WLAN (Wireless Local area Network) , BlueTooth, In- frared, and the like may be used; although the above tech^¬ nologies are mostly wireless access technologies, e.g. in different radio spectra, access technology in the sense of the present invention may also imply wirebound technologies, e.g. IP based access technologies like cable networks or fixed line.

- a network may be any device, unit or means by which a sta^¬ tion entity or other user equipment may connect to and/or utilize services offered by the access network; such services include, among others, data and/or (audio-) visual communica- tion, data download etc.;

- generally, the present invention may be applicable in those network/user equipment environments relying on a data packet based transmission scheme according to which data are transmitted in data packets and which are, for example, based on the internet protocol (IP) . The present invention is, how^¬ ever, not limited thereto, and any other present or future IP or mobile IP (MIP) version, or, more generally, a protocol following similar principles as (M)IPv4/6, is also applica^¬ ble;

- a user equipment may be any device, unit or means by which a system user may experience services from an access network;

- method steps likely to be implemented as software code portions and being run using a processor at a network element or terminal (as examples of devices, apparatuses and/or mod- ules thereof, or as examples of entities including appara^¬ tuses, circuitries and/or modules therefore), are software code independent and can be specified using any known or fu^¬ ture developed programming language as long as the function^¬ ality defined by the method steps is preserved;

- generally, any method step is suitable to be implemented as software or by hardware without changing the idea of the in^¬ vention in terms of the functionality implemented;

- method steps and/or devices, units or means likely to be implemented as hardware components at the above-defined appa^¬ ratuses, or any module ( s ) /circuitry ( ies ) thereof, are hard- ware independent and can be implemented using any known or future developed hardware technology or any hybrids of these, such as MOS (Metal Oxide Semiconductor) , CMOS (Complementary MOS), BiMOS (Bipolar MOS), BiCMOS (Bipolar CMOS), ECL (Emit^¬ ter Coupled Logic), TTL (Transistor-Transistor Logic), etc., using for example ASIC (Application Specific IC (Integrated Circuit) ) components, FPGA (Field-programmable Gate Arrays) components, CPLD (Complex Programmable Logic Device) compo^¬ nents or DSP (Digital Signal Processor) components; in addi^¬ tion, any method steps and/or devices, units or means likely to be implemented as software components may alternatively be based on any security architecture capable e.g. of authenti^¬ cation, authorization, keying and/or traffic protection;

- devices, units, circuitries or means (e.g. the above- defined apparatuses, or any one of their respective means) can be implemented as individual devices, units or means, but this does not exclude that they are implemented in a distrib^¬ uted fashion throughout the system, as long as the functionality of the device, unit, circuitry or means is preserved;

- an apparatus may be represented by a semiconductor chip, a chipset, a (hardware) module comprising such chip or chipset, or a circuitry; this, however, does not exclude the possibil^¬ ity that a functionality of an apparatus, module or cir^¬ cuitry, instead of being hardware implemented, be implemented as software in a (software) module such as a computer program or a computer program product comprising executable software code portions for execution/being run on a processor; - a device may be regarded as an apparatus or as an assembly of more than one apparatus, whether functionally in coopera^¬ tion with each other or functionally independently of each other but in a same device housing, for example.

According to an aspect of the present invention, an apparatus such as an MME comprises a receiver 20214 configured to re^¬ ceive coding/decoding information (e.g. selected IMS codec) currently selected according to a first communication tech- nology (e.g. IMS), a decider 20215 configured to decide on whether a handover operation (e.g. SRVCC handover) from the first technology to a second technology (e.g. CS) different from the first technology is to be performed, and a transmit^¬ ter 20213 configured to transmit, if the deciding is affirma- tive, a request (e.g. Fwd Relocation request) comprising the coding/decoding information currently selected.

The apparatus may further comprise a memory 20212 configured to store the coding/decoding information currently selected.

According to an aspect of the invention, an apparatus such as a P-CSCF/AF, PCRF or PDN-GW/S-GW comprises a transmitter 20243, 20233 configured to transmit coding/decoding informa^¬ tion (e.g. selected IMS codec) currently selected according to a first communication technology (e.g. IMS), the cod^¬ ing/decoding information being intended for use during a handover procedure from the first technology to a second technology (e.g. CS) different from the first technology. The coding/decoding information currently selected may constitute a first applied content of a service-to-access- control container.

The service-to-access-control container may be transmitted and received transparently. The apparatus may further comprise a determiner 20245 config^¬ ured to determine, if the coding/decoding information currently selected cannot be determined, to use, as the cod^¬ ing/decoding information currently selected, the first common coding/decoding information according to a session description protocol offer and answer scheme.

The apparatus may further comprise means a transmitter 20243 configured to transmit more than one candidate for the cod- ing/decoding information currently selected.

According to an aspect of the invention, an apparatus such as an MSS comprises a receiver 20264 configured to receive a re^¬ quest (e.g. Fwd Relocation request) comprising cod- ing/decoding information currently selected according to a first communication technology (e.g. IMS) depending on a de^¬ cision on whether a handover operation from the first technology to a second technology (e.g. CS) different from the first technology is to be performed, and a reserver 20265 configured to reserve at least one communication resource

(e.g. bearer) of the second technology according to the cod^¬ ing/decoding information currently selected.

The transmitter and the receiver of the coding/decoding in- formation currently selected may be configured to perform transmitting and receiving based on policy and charging control-related interfaces and/or evolved packet core inter^¬ faces . The policy and charging control-related interfaces and/or evolved packet core interfaces may comprise at least one of the Rx, Gx, Gxx, S5/S8, Sll and S9 interfaces.

At least one of the following may apply:

the coding/decoding information is constituted by internet protocol multimedia subsystem codec information; the first communication technology is constituted by an internet protocol multimedia subsystem;

the second communication technology is constituted by a circuit switched mobile network;

the handover operation is constituted by a single ra^¬ dio voice call continuity handover operation; and

the request is constituted by a forward relocation re^¬ quest . At least one or more of the receivers, decider, transmitters, memories, determiner, reserver and the apparatuses may be im^¬ plemented as a chipset, module or subassembly.

A network entity 2023, 2024 transmits coding/decoding infor- mation currently selected according to a first communication technology, the coding/decoding information being intended for use in a handover procedure from the first technology to a second technology different from the first technology. A network entity 2021 receives (S4-1) the coding/decoding in- formation currently selected according to the first communi^¬ cation technology. In case a handover operation from the first technology to the second technology is decided (S4-3) to be performed, a request comprising the coding/decoding information currently selected is transmitted (S4-4) . The re- quest is received (S5-1) by a network entity 2026, which re^¬ serves (S5-2) at least one communication resource of the sec^¬ ond technology according to the coding/decoding information currently selected. According to an aspect, the present invention may be imple^¬ mented as computer program product which includes a program for a processing device (e.g. at lest one of the CPUs shown in Fig. 5, wherein the program may be stored in at least one of the memories shown in Fig. 5), comprising software code portions for performing the steps of the appended method claims when the program is run on the processing device. The computer program product may comprise a computer-readable me dium on which the software code portions are stored, and/or the program may be directly loadable into an internal memory of the processing device.

Although the present invention has been described herein before with reference to particular embodiments thereof, the present invention is not limited thereto and various modifi^¬ cation can be made thereto.

Claims

CLAIMS :

1. A method, comprising:

receiving coding/decoding information currently se- lected according to a first communication technology;

deciding on whether a handover operation from the first technology to a second technology different from the first technology is to be performed; and

transmitting, if the deciding is affirmative, a re- quest comprising the coding/decoding information currently selected .

2. The method according to claim 1, further comprising storing the coding/decoding information currently selected.

3. A method, comprising:

transmitting coding/decoding information currently selected according to a first communication technology, the coding/decoding information being intended for use in a hand- over procedure from the first technology to a second technol^¬ ogy different from the first technology.

4. The method according to claims 1 and 3, wherein the cod^¬ ing/decoding information currently selected constitute a first applied content of a service-to-access-control con^¬ tainer .

5. The method according to claim 4, wherein the service-to- access-control container is transmitted and received trans- parently.

6. The method according to claim 3, further comprising determining, if the coding/decoding information currently selected cannot be determined, to use, as the coding/decoding informa- tion currently selected, the first common coding/decoding in- formation according to a session description protocol offer and answer scheme.

7. The method according to claim 3, further comprising trans- mitting more than one candidate for the coding/decoding information currently selected.

8. A method, comprising:

receiving a request comprising coding/decoding infor- mation currently selected according to a first communication technology depending on a decision on whether a handover operation from the first technology to a second technology dif^¬ ferent from the first technology is to be performed; and

reserving at least one communication resource of the second technology according to the coding/decoding informa^¬ tion currently selected.

9. The method according to claim 1, 3 and 8, wherein the transmitting and receiving of the coding/decoding information currently selected is performed based on policy and charging control-related interfaces and/or evolved packet core related interfaces .

10. The method according to claim 9, wherein the policy and charging control-related interfaces and/or evolved packet core related interfaces comprise at least one of the Rx, Gx, Gxx, S5/S8, Sll and S9 interfaces.

11. The method according to any one of claims 1 to 10, wherein at least one of the following applies:

the coding/decoding information is constituted by internet protocol multimedia subsystem codec information;

the first communication technology is constituted by an internet protocol multimedia subsystem;

the second communication technology is constituted by a circuit switched mobile network; the handover operation is constituted by a single ra^¬ dio voice call continuity handover operation; and

the request is constituted by a forward relocation re^¬ quest .

12. An apparatus, comprising:

means for receiving coding/decoding information currently selected according to a first communication technol^¬ ogy;

means for deciding on whether a handover operation from the first technology to a second technology different from the first technology is to be performed; and

means for transmitting, if the deciding is affirmative, a request comprising the coding/decoding information currently selected.

13. The apparatus according to claim 12, further comprising means for storing the coding/decoding information currently selected .

14. An apparatus, comprising:

means for transmitting coding/decoding information currently selected according to a first communication technology, the coding/decoding information being intended for use in a handover procedure from the first technology to a second technology different from the first technology.

15. The apparatus according to claims 12 and 14, wherein the coding/decoding information currently selected constitute a first applied content of a service-to-access-control con^¬ tainer .

16. The apparatus according to claim 15, wherein the service- to-access-control container is transmitted and received transparently.

17. The apparatus according to claim 14, further comprising means for determining, if the coding/decoding information currently selected cannot be determined, to use, as the cod^¬ ing/decoding information currently selected, the first common coding/decoding information according to a session description protocol offer and answer scheme.

18. The apparatus according to claim 14, further comprising means for transmitting more than one candidate for the cod- ing/decoding information currently selected.

19. An apparatus, comprising:

means for receiving a request comprising coding/decoding information currently selected according to a first communication technology depending on a decision on whether a handover operation from the first technology to a second technology different from the first technology is to be performed; and

means for reserving at least one communication re- source of the second technology according to the cod^¬ ing/decoding information currently selected.

20. The apparatus according to claim 12, 14 and 19, wherein the means for transmitting and the means for receiving of the coding/decoding information currently selected perform transmitting and receiving based on policy and charging control- related interfaces and/or evolved packet core related inter^¬ faces .

21. The apparatus according to claim 20, wherein the policy and charging control-related interfaces and/or evolved packet core related interfaces comprise at least one of the Rx, Gx, Gxx, S5/S8, Sll and S9 interfaces.

22. The apparatus according to any one of claims 12 to 21, wherein at least one of the following applies: the coding/decoding information is constituted by internet protocol multimedia subsystem codec information;

the request is constituted by a forward relocation re- quest.

23. The apparatus according to claim 12, wherein the appara^¬ tus is constituted by a mobility management entity.

24. The apparatus according to claim 14, wherein the apparatus is constituted by one of a proxy call service control function or application function, a policy charging rules function and a packet data network gateway or serving gate^¬ way .

25. The apparatus according to claim 19, wherein the appara^¬ tus is constituted by a mobile switching center server.

26. The apparatus according to any one of claims 12 to 25, wherein at least one, or more of means for receiving, means for deciding, means for transmitting, means for storing, means for determining, means for reserving and the apparatus is implemented as a chipset, module or subassembly.

27. A computer program product comprising code means for performing a method according to any one of claims 1 to 11 when run on a processing means or module.